Usefulness of ICD electrograms analysis to distinguish endocardial vs epicardial ventricular tachycardia in arrhythmogenic right ventricular cardiomyopathy

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by an epicardial (EPI) to endocardial (ENDO) fibrofatty infiltration of the RV predisposing to both EPI and ENDO ventricular tachycardia (VT). The relative timing between the VT QRS onset on the far-field ventricular electrogram (VEGM) to the local activation time recorded at the RV apex on the near-field VEGM from stored implantable cardioverter-defibrillator (ICD) events of VT can be helpful to discriminate ENDO from EPI VT in ARVC. Methods and results: We analyzed consecutive ARVC patients undergoing catheter ablation between 2006 and 2018. Only patients with retrievable ICD VEGMs of clinical VTs which could be matched with VTs induced at the time of ablation were included. A total of 26 VT events (16 ENDO, 10 EPI) from 19 ARVC patients were examined, yielding a mean far-field to near-field interval of 33 ± 15 ms for ENDO VTs and 52 ± 20 ms for EPI VTs (P =.020). At receiver-operating characteristic analysis, a far-field to a near-field interval of 60 ms or more ruled out ENDO VTs in 16 (100%) cases and identified EPI VTs with a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 73%. An interval of less than or equal to 30 ms ruled out EPI VTs in eight (80%) cases and diagnosed ENDO VTs with a PPV of 80% and an NPV of 50%. Conclusion: Far-field to near-field ICD VEGM timing may be used to predict ENDO vs EPI VT in ARVC before ablation, indicating an ENDO origin if the timing is less than or equal to 30 ms and an EPI origin if greater than or equal to 60 ms.